1,044 research outputs found
MHD simulations of dense core collision
We investigated the effect of magnetic fields on the collision process
between dense molecular cores. We performed three-dimensional
magnetohydrodynamic simulations of collisions between two self-gravitating
cores using the Enzo adaptive mesh refinement code. The core was modeled as a
stable isothermal Bonnor-Ebert (BE) sphere immersed in uniform magnetic fields.
Collisions were characterized by the offset parameter , Mach number of the
initial core , magnetic field strength , and angle
between the initial magnetic field and collision axis. For head-on ()
collisions, one protostar was formed in the compressed layer. The higher the
magnetic field strength, the lower the accretion rate. For models with
and , the accretion rate was more dependent on the initial
magnetic field strength compared with and models.
For off-center () collisions, the higher specific angular momentum
increased; therefore, the gas motion was complicated. In models with
and , the number of protostars and gas motion highly depended
on and . For models with and , no
significant shock-compressed layer was formed and star formation was not
triggered.Comment: 20 pages, 18 figures, 3 tables. Accepted for publication in Ap
Unveiling the Dynamics of Dense Cores in Cluster-Forming Clumps: A 3D MHD Simulation Study of Angular Momentum and Magnetic Field Properties
We conducted isothermal MHD simulations with self-gravity to investigate the
properties of dense cores in cluster-forming clumps. Two different setups were
explored: a single rotating clump and colliding clumps. We focused on
determining the extent to which the formed dense cores inherit the rotation and
magnetic field of the parental clump. Our statistical analysis revealed that
the alignment between the angular momentum of dense cores, ,
and the rotational axis of the clump is influenced by the strength of
turbulence and the simulation setup. In single rotating clumps, we found that
tends to align with the clump's rotational axis if the
initial turbulence is weak. However, in colliding clumps, this alignment does
not occur, regardless of the initial turbulence strength. This misalignment in
colliding clumps is due to the induced turbulence from the collision and the
isotropic gas inflow into dense cores. Our analysis of colliding clumps also
revealed that the magnetic field globally bends along the shock-compressed
layer, and the mean magnetic field of dense cores, , aligns
with it. Both in single rotating clumps and colliding clumps, we found that the
angle between and is generally random,
regardless of the clump properties. We also analyzed the dynamical states of
the formed cores and found a higher proportion of unbound cores in colliding
clumps. In addition, the contribution of rotational energy was only
approximately 5% of the gravitational energy, regardless of the model
parameters for both single and colliding cases.Comment: 28 pages, 25 figures, 3 tables. Accepted for publication in Ap
Precise Orbit Determination for ALOS
The Advanced Land Observing Satellite (ALOS) has been developed to contribute to the fields of mapping, precise regional land coverage observation, disaster monitoring, and resource surveying. Because the mounted sensors need high geometrical accuracy, precise orbit determination for ALOS is essential for satisfying the mission objectives. So ALOS mounts a GPS receiver and a Laser Reflector (LR) for Satellite Laser Ranging (SLR). This paper deals with the precise orbit determination experiments for ALOS using Global and High Accuracy Trajectory determination System (GUTS) and the evaluation of the orbit determination accuracy by SLR data. The results show that, even though the GPS receiver loses lock of GPS signals more frequently than expected, GPS-based orbit is consistent with SLR-based orbit. And considering the 1 sigma error, orbit determination accuracy of a few decimeters (peak-to-peak) was achieved
HPLC Analysis of Homocysteine and Related Compounds
Homocysteine (Hcy), a sulfur-containing amino acid, is a representative intermediate metabolite of methionine (Met) to cysteine (Cys) via several intermediates. An elevated level of Hcy in plasma plays an important role in diseases such as neural tube defects and Down syndrome. Homocystinuria is the most common inborn error of sulfur metabolism and is caused by mutations in the metabolic enzymes of Hcy. These errors can be caused by abnormal levels of Met metabolites and classified on the basis of plasma Met levels. Additionally, Hcy and related compounds such as glutathione play an important role in maintaining homeostasis. Therefore, the simultaneous determination of Hcy and/or related compounds is required for appropriate clinical management of several diseases. The sulfur-containing amino acids and their derivatives in biological samples are quantified sensitively using high-performance liquid chromatography methods coupled with various detection methods such as UV/Vis, fluorescence, chemiluminescence, electrochemical, mass spectrometry, and tandem mass spectrometry. In this chapter, we review recent advances in these analytical methods and their applications
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